The operation of most agricultural vehicles requires substantial operational involvement and control by the operator. For example, in a combine the operator is required to control the direction and speed of the combine while also controlling the height of the combine head, the air flow through the combine cleaning fan, and the amount of harvested crop stored on the combine. Accordingly, to reduce the effort required by the operator, it is useful to automate as many tasks performed by the operator as possible.
One task which has been automated is maintaining the distance between the harvesting implement (head) of a combine and the ground. More specifically, some combines include control systems which permit an operator to control and maintain a selected distance between the head and ground during harvesting and without further interaction by the operator. This control is based upon monitoring one or two transducers which produce signals representative of the distance between the head and ground.
A problem with such prior systems for automatically controlling harvesting head height is that the fields are normally uneven and a single sensor will not sense the minimum distance to ground, thus, frequently resulting in head-to-ground contact. Furthermore, even if one were to use more than one sensor along the head to sense a plurality of ground heights, the control system would be required to monitor a plurality of ground height signals to provide automatic control thereof.
Accordingly, it would be desirable to provide a ground height sensing arrangement which includes distance sensors at the ends and center of a head, and additional distance sensors depending upon the width of the head (e.g. a 30-foot wide head may require 4 or more sensors). Furthermore, the arrangement should be configured to produce only a single distance signal representative of the smallest distance between the head and ground.